The hedge fund manager at the heart of the government’s insider-trading case against Galleon Group founder Raj Rajaratnam has been identified as Thomas Hardin.

Hardin, a former trader at hedge fund Lanexa Global Management and an associate of hedge fund legend Julian Robertson, is the person identified as “Tipper X” in a Securities and Exchange Commission complaint filed in November. Tipper X was described as the link between the two insider-trading rings in a case that has produced charges against 21 people and seven guilty pleas.

Hardin has not been charged with any wrongdoing. But the SEC complaint alleges that he both shared and traded on nonpublic information about a variety of companies, including Google Inc., Hilton Hotels and Kronos Inc. Rajaratnam is also accused of illegal trading of Google and Hilton shares.

Hardin is also linked to Roomy Khan, the government’s star witness against Rajaratnam. According to the SEC, Hardin helped Kahn pay sources for tips.

Lanexa, a New York-based technology hedge fund with about $95 million in assets under management, fired Hardin last January, Bloomberg News reports. A spokesman for the hedge fund said he was “terminated for performance.”

Though Hardin’s insider-trading allegedly occurred while he was at Lanexa, the hedge fund has not been charged with any wrongdoing. But Ian Murray, the firm’s CEO, was listed among potential witnesses this week by prosecutors. Murray formerly worked at Narragansett Asset Management and Straus Asset Management. He has also not been accused of any wrongdoing.